kernel/fs/cachefiles/interface.c

   1 /* FS-Cache interface to CacheFiles
   2  *
   3  * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
   4  * Written by David Howells (dhowells@redhat.com)
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public Licence
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the Licence, or (at your option) any later version.
  10  */
  11
  12 #include <linux/slab.h>
  13 #include <linux/mount.h>
  14 #include "internal.h"
  15
  16 struct cachefiles_lookup_data {
  17         struct cachefiles_xattr *auxdata;       /* auxiliary data */
  18         char                    *key;           /* key path */
  19 };
  20
  21 static int cachefiles_attr_changed(struct fscache_object *_object);
  22
  23 /*
  24  * allocate an object record for a cookie lookup and prepare the lookup data
  25  */
  26 static struct fscache_object *cachefiles_alloc_object(
  27         struct fscache_cache *_cache,
  28         struct fscache_cookie *cookie)
  29 {
  30         struct cachefiles_lookup_data *lookup_data;
  31         struct cachefiles_object *object;
  32         struct cachefiles_cache *cache;
  33         struct cachefiles_xattr *auxdata;
  34         unsigned keylen, auxlen;
  35         void *buffer;
  36         char *key;
  37
  38         cache = container_of(_cache, struct cachefiles_cache, cache);
  39
  40         _enter("{%s},%p,", cache->cache.identifier, cookie);
  41
  42         lookup_data = kmalloc(sizeof(*lookup_data), cachefiles_gfp);
  43         if (!lookup_data)
  44                 goto nomem_lookup_data;
  45
  46         /* create a new object record and a temporary leaf image */
  47         object = kmem_cache_alloc(cachefiles_object_jar, cachefiles_gfp);
  48         if (!object)
  49                 goto nomem_object;
  50
  51         ASSERTCMP(object->backer, ==, NULL);
  52
  53         BUG_ON(test_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags));
  54         atomic_set(&object->usage, 1);
  55
  56         fscache_object_init(&object->fscache, cookie, &cache->cache);
  57
  58         object->type = cookie->def->type;
  59
  60         /* get hold of the raw key
  61          * - stick the length on the front and leave space on the back for the
  62          *   encoder
  63          */
  64         buffer = kmalloc((2 + 512) + 3, cachefiles_gfp);
  65         if (!buffer)
  66                 goto nomem_buffer;
  67
  68         keylen = cookie->def->get_key(cookie->netfs_data, buffer + 2, 512);
  69         ASSERTCMP(keylen, <, 512);
  70
  71         *(uint16_t *)buffer = keylen;
  72         ((char *)buffer)[keylen + 2] = 0;
  73         ((char *)buffer)[keylen + 3] = 0;
  74         ((char *)buffer)[keylen + 4] = 0;
  75
  76         /* turn the raw key into something that can work with as a filename */
  77         key = cachefiles_cook_key(buffer, keylen + 2, object->type);
  78         if (!key)
  79                 goto nomem_key;
  80
  81         /* get hold of the auxiliary data and prepend the object type */
  82         auxdata = buffer;
  83         auxlen = 0;
  84         if (cookie->def->get_aux) {
  85                 auxlen = cookie->def->get_aux(cookie->netfs_data,
  86                                               auxdata->data, 511);
  87                 ASSERTCMP(auxlen, <, 511);
  88         }
  89
  90         auxdata->len = auxlen + 1;
  91         auxdata->type = cookie->def->type;
  92
  93         lookup_data->auxdata = auxdata;
  94         lookup_data->key = key;
  95         object->lookup_data = lookup_data;
  96
  97         _leave(" = %p [%p]", &object->fscache, lookup_data);
  98         return &object->fscache;
  99
 100 nomem_key:
 101         kfree(buffer);
 102 nomem_buffer:
 103         BUG_ON(test_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags));
 104         kmem_cache_free(cachefiles_object_jar, object);
 105         fscache_object_destroyed(&cache->cache);
 106 nomem_object:
 107         kfree(lookup_data);
 108 nomem_lookup_data:
 109         _leave(" = -ENOMEM");
 110         return ERR_PTR(-ENOMEM);
 111 }
 112
 113 /*
 114  * attempt to look up the nominated node in this cache
 115  * - return -ETIMEDOUT to be scheduled again
 116  */
 117 static int cachefiles_lookup_object(struct fscache_object *_object)
 118 {
 119         struct cachefiles_lookup_data *lookup_data;
 120         struct cachefiles_object *parent, *object;
 121         struct cachefiles_cache *cache;
 122         const struct cred *saved_cred;
 123         int ret;
 124
 125         _enter("{OBJ%x}", _object->debug_id);
 126
 127         cache = container_of(_object->cache, struct cachefiles_cache, cache);
 128         parent = container_of(_object->parent,
 129                               struct cachefiles_object, fscache);
 130         object = container_of(_object, struct cachefiles_object, fscache);
 131         lookup_data = object->lookup_data;
 132
 133         ASSERTCMP(lookup_data, !=, NULL);
 134
 135         /* look up the key, creating any missing bits */
 136         cachefiles_begin_secure(cache, &saved_cred);
 137         ret = cachefiles_walk_to_object(parent, object,
 138                                         lookup_data->key,
 139                                         lookup_data->auxdata);
 140         cachefiles_end_secure(cache, saved_cred);
 141
 142         /* polish off by setting the attributes of non-index files */
 143         if (ret == 0 &&
 144             object->fscache.cookie->def->type != FSCACHE_COOKIE_TYPE_INDEX)
 145                 cachefiles_attr_changed(&object->fscache);
 146
 147         if (ret < 0 && ret != -ETIMEDOUT) {
 148                 if (ret != -ENOBUFS)
 149                         pr_warn("Lookup failed error %d\n", ret);
 150                 fscache_object_lookup_error(&object->fscache);
 151         }
 152
 153         _leave(" [%d]", ret);
 154         return ret;
 155 }
 156
 157 /*
 158  * indication of lookup completion
 159  */
 160 static void cachefiles_lookup_complete(struct fscache_object *_object)
 161 {
 162         struct cachefiles_object *object;
 163
 164         object = container_of(_object, struct cachefiles_object, fscache);
 165
 166         _enter("{OBJ%x,%p}", object->fscache.debug_id, object->lookup_data);
 167
 168         if (object->lookup_data) {
 169                 kfree(object->lookup_data->key);
 170                 kfree(object->lookup_data->auxdata);
 171                 kfree(object->lookup_data);
 172                 object->lookup_data = NULL;
 173         }
 174 }
 175
 176 /*
 177  * increment the usage count on an inode object (may fail if unmounting)
 178  */
 179 static
 180 struct fscache_object *cachefiles_grab_object(struct fscache_object *_object)
 181 {
 182         struct cachefiles_object *object =
 183                 container_of(_object, struct cachefiles_object, fscache);
 184
 185         _enter("{OBJ%x,%d}", _object->debug_id, atomic_read(&object->usage));
 186
 187 #ifdef CACHEFILES_DEBUG_SLAB
 188         ASSERT((atomic_read(&object->usage) & 0xffff0000) != 0x6b6b0000);
 189 #endif
 190
 191         atomic_inc(&object->usage);
 192         return &object->fscache;
 193 }
 194
 195 /*
 196  * update the auxiliary data for an object object on disk
 197  */
 198 static void cachefiles_update_object(struct fscache_object *_object)
 199 {
 200         struct cachefiles_object *object;
 201         struct cachefiles_xattr *auxdata;
 202         struct cachefiles_cache *cache;
 203         struct fscache_cookie *cookie;
 204         const struct cred *saved_cred;
 205         unsigned auxlen;
 206
 207         _enter("{OBJ%x}", _object->debug_id);
 208
 209         object = container_of(_object, struct cachefiles_object, fscache);
 210         cache = container_of(object->fscache.cache, struct cachefiles_cache,
 211                              cache);
 212
 213         if (!fscache_use_cookie(_object)) {
 214                 _leave(" [relinq]");
 215                 return;
 216         }
 217
 218         cookie = object->fscache.cookie;
 219
 220         if (!cookie->def->get_aux) {
 221                 fscache_unuse_cookie(_object);
 222                 _leave(" [no aux]");
 223                 return;
 224         }
 225
 226         auxdata = kmalloc(2 + 512 + 3, cachefiles_gfp);
 227         if (!auxdata) {
 228                 fscache_unuse_cookie(_object);
 229                 _leave(" [nomem]");
 230                 return;
 231         }
 232
 233         auxlen = cookie->def->get_aux(cookie->netfs_data, auxdata->data, 511);
 234         fscache_unuse_cookie(_object);
 235         ASSERTCMP(auxlen, <, 511);
 236
 237         auxdata->len = auxlen + 1;
 238         auxdata->type = cookie->def->type;
 239
 240         cachefiles_begin_secure(cache, &saved_cred);
 241         cachefiles_update_object_xattr(object, auxdata);
 242         cachefiles_end_secure(cache, saved_cred);
 243         kfree(auxdata);
 244         _leave("");
 245 }
 246
 247 /*
 248  * discard the resources pinned by an object and effect retirement if
 249  * requested
 250  */
 251 static void cachefiles_drop_object(struct fscache_object *_object)
 252 {
 253         struct cachefiles_object *object;
 254         struct cachefiles_cache *cache;
 255         const struct cred *saved_cred;
 256
 257         ASSERT(_object);
 258
 259         object = container_of(_object, struct cachefiles_object, fscache);
 260
 261         _enter("{OBJ%x,%d}",
 262                object->fscache.debug_id, atomic_read(&object->usage));
 263
 264         cache = container_of(object->fscache.cache,
 265                              struct cachefiles_cache, cache);
 266
 267 #ifdef CACHEFILES_DEBUG_SLAB
 268         ASSERT((atomic_read(&object->usage) & 0xffff0000) != 0x6b6b0000);
 269 #endif
 270
 271         /* We need to tidy the object up if we did in fact manage to open it.
 272          * It's possible for us to get here before the object is fully
 273          * initialised if the parent goes away or the object gets retired
 274          * before we set it up.
 275          */
 276         if (object->dentry) {
 277                 /* delete retired objects */
 278                 if (test_bit(FSCACHE_OBJECT_RETIRED, &object->fscache.flags) &&
 279                     _object != cache->cache.fsdef
 280                     ) {
 281                         _debug("- retire object OBJ%x", object->fscache.debug_id);
 282                         cachefiles_begin_secure(cache, &saved_cred);
 283                         cachefiles_delete_object(cache, object);
 284                         cachefiles_end_secure(cache, saved_cred);
 285                 }
 286
 287                 /* close the filesystem stuff attached to the object */
 288                 if (object->backer != object->dentry)
 289                         dput(object->backer);
 290                 object->backer = NULL;
 291         }
 292
 293         /* note that the object is now inactive */
 294         if (test_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags)) {
 295                 write_lock(&cache->active_lock);
 296                 if (!test_and_clear_bit(CACHEFILES_OBJECT_ACTIVE,
 297                                         &object->flags))
 298                         BUG();
 299                 rb_erase(&object->active_node, &cache->active_nodes);
 300                 wake_up_bit(&object->flags, CACHEFILES_OBJECT_ACTIVE);
 301                 write_unlock(&cache->active_lock);
 302         }
 303
 304         dput(object->dentry);
 305         object->dentry = NULL;
 306
 307         _leave("");
 308 }
 309
 310 /*
 311  * dispose of a reference to an object
 312  */
 313 static void cachefiles_put_object(struct fscache_object *_object)
 314 {
 315         struct cachefiles_object *object;
 316         struct fscache_cache *cache;
 317
 318         ASSERT(_object);
 319
 320         object = container_of(_object, struct cachefiles_object, fscache);
 321
 322         _enter("{OBJ%x,%d}",
 323                object->fscache.debug_id, atomic_read(&object->usage));
 324
 325 #ifdef CACHEFILES_DEBUG_SLAB
 326         ASSERT((atomic_read(&object->usage) & 0xffff0000) != 0x6b6b0000);
 327 #endif
 328
 329         ASSERTIFCMP(object->fscache.parent,
 330                     object->fscache.parent->n_children, >, 0);
 331
 332         if (atomic_dec_and_test(&object->usage)) {
 333                 _debug("- kill object OBJ%x", object->fscache.debug_id);
 334
 335                 ASSERT(!test_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags));
 336                 ASSERTCMP(object->fscache.parent, ==, NULL);
 337                 ASSERTCMP(object->backer, ==, NULL);
 338                 ASSERTCMP(object->dentry, ==, NULL);
 339                 ASSERTCMP(object->fscache.n_ops, ==, 0);
 340                 ASSERTCMP(object->fscache.n_children, ==, 0);
 341
 342                 if (object->lookup_data) {
 343                         kfree(object->lookup_data->key);
 344                         kfree(object->lookup_data->auxdata);
 345                         kfree(object->lookup_data);
 346                         object->lookup_data = NULL;
 347                 }
 348
 349                 cache = object->fscache.cache;
 350                 fscache_object_destroy(&object->fscache);
 351                 kmem_cache_free(cachefiles_object_jar, object);
 352                 fscache_object_destroyed(cache);
 353         }
 354
 355         _leave("");
 356 }
 357
 358 /*
 359  * sync a cache
 360  */
 361 static void cachefiles_sync_cache(struct fscache_cache *_cache)
 362 {
 363         struct cachefiles_cache *cache;
 364         const struct cred *saved_cred;
 365         int ret;
 366
 367         _enter("%p", _cache);
 368
 369         cache = container_of(_cache, struct cachefiles_cache, cache);
 370
 371         /* make sure all pages pinned by operations on behalf of the netfs are
 372          * written to disc */
 373         cachefiles_begin_secure(cache, &saved_cred);
 374         down_read(&cache->mnt->mnt_sb->s_umount);
 375         ret = sync_filesystem(cache->mnt->mnt_sb);
 376         up_read(&cache->mnt->mnt_sb->s_umount);
 377         cachefiles_end_secure(cache, saved_cred);
 378
 379         if (ret == -EIO)
 380                 cachefiles_io_error(cache,
 381                                     "Attempt to sync backing fs superblock"
 382                                     " returned error %d",
 383                                     ret);
 384 }
 385
 386 /*
 387  * check if the backing cache is updated to FS-Cache
 388  * - called by FS-Cache when evaluates if need to invalidate the cache
 389  */
 390 static bool cachefiles_check_consistency(struct fscache_operation *op)
 391 {
 392         struct cachefiles_object *object;
 393         struct cachefiles_cache *cache;
 394         const struct cred *saved_cred;
 395         int ret;
 396
 397         _enter("{OBJ%x}", op->object->debug_id);
 398
 399         object = container_of(op->object, struct cachefiles_object, fscache);
 400         cache = container_of(object->fscache.cache,
 401                              struct cachefiles_cache, cache);
 402
 403         cachefiles_begin_secure(cache, &saved_cred);
 404         ret = cachefiles_check_auxdata(object);
 405         cachefiles_end_secure(cache, saved_cred);
 406
 407         _leave(" = %d", ret);
 408         return ret;
 409 }
 410
 411 /*
 412  * notification the attributes on an object have changed
 413  * - called with reads/writes excluded by FS-Cache
 414  */
 415 static int cachefiles_attr_changed(struct fscache_object *_object)
 416 {
 417         struct cachefiles_object *object;
 418         struct cachefiles_cache *cache;
 419         const struct cred *saved_cred;
 420         struct iattr newattrs;
 421         uint64_t ni_size;
 422         loff_t oi_size;
 423         int ret;
 424
 425         _object->cookie->def->get_attr(_object->cookie->netfs_data, &ni_size);
 426
 427         _enter("{OBJ%x},[%llu]",
 428                _object->debug_id, (unsigned long long) ni_size);
 429
 430         object = container_of(_object, struct cachefiles_object, fscache);
 431         cache = container_of(object->fscache.cache,
 432                              struct cachefiles_cache, cache);
 433
 434         if (ni_size == object->i_size)
 435                 return 0;
 436
 437         if (!object->backer)
 438                 return -ENOBUFS;
 439
 440         ASSERT(d_is_reg(object->backer));
 441
 442         fscache_set_store_limit(&object->fscache, ni_size);
 443
 444         oi_size = i_size_read(d_backing_inode(object->backer));
 445         if (oi_size == ni_size)
 446                 return 0;
 447
 448         cachefiles_begin_secure(cache, &saved_cred);
 449         mutex_lock(&d_inode(object->backer)->i_mutex);
 450
 451         /* if there's an extension to a partial page at the end of the backing
 452          * file, we need to discard the partial page so that we pick up new
 453          * data after it */
 454         if (oi_size & ~PAGE_MASK && ni_size > oi_size) {
 455                 _debug("discard tail %llx", oi_size);
 456                 newattrs.ia_valid = ATTR_SIZE;
 457                 newattrs.ia_size = oi_size & PAGE_MASK;
 458                 ret = notify_change(object->backer, &newattrs, NULL);
 459                 if (ret < 0)
 460                         goto truncate_failed;
 461         }
 462
 463         newattrs.ia_valid = ATTR_SIZE;
 464         newattrs.ia_size = ni_size;
 465         ret = notify_change(object->backer, &newattrs, NULL);
 466
 467 truncate_failed:
 468         mutex_unlock(&d_inode(object->backer)->i_mutex);
 469         cachefiles_end_secure(cache, saved_cred);
 470
 471         if (ret == -EIO) {
 472                 fscache_set_store_limit(&object->fscache, 0);
 473                 cachefiles_io_error_obj(object, "Size set failed");
 474                 ret = -ENOBUFS;
 475         }
 476
 477         _leave(" = %d", ret);
 478         return ret;
 479 }
 480
 481 /*
 482  * Invalidate an object
 483  */
 484 static void cachefiles_invalidate_object(struct fscache_operation *op)
 485 {
 486         struct cachefiles_object *object;
 487         struct cachefiles_cache *cache;
 488         const struct cred *saved_cred;
 489         struct path path;
 490         uint64_t ni_size;
 491         int ret;
 492
 493         object = container_of(op->object, struct cachefiles_object, fscache);
 494         cache = container_of(object->fscache.cache,
 495                              struct cachefiles_cache, cache);
 496
 497         op->object->cookie->def->get_attr(op->object->cookie->netfs_data,
 498                                           &ni_size);
 499
 500         _enter("{OBJ%x},[%llu]",
 501                op->object->debug_id, (unsigned long long)ni_size);
 502
 503         if (object->backer) {
 504                 ASSERT(d_is_reg(object->backer));
 505
 506                 fscache_set_store_limit(&object->fscache, ni_size);
 507
 508                 path.dentry = object->backer;
 509                 path.mnt = cache->mnt;
 510
 511                 cachefiles_begin_secure(cache, &saved_cred);
 512                 ret = vfs_truncate(&path, 0);
 513                 if (ret == 0)
 514                         ret = vfs_truncate(&path, ni_size);
 515                 cachefiles_end_secure(cache, saved_cred);
 516
 517                 if (ret != 0) {
 518                         fscache_set_store_limit(&object->fscache, 0);
 519                         if (ret == -EIO)
 520                                 cachefiles_io_error_obj(object,
 521                                                         "Invalidate failed");
 522                 }
 523         }
 524
 525         fscache_op_complete(op, true);
 526         _leave("");
 527 }
 528
 529 /*
 530  * dissociate a cache from all the pages it was backing
 531  */
 532 static void cachefiles_dissociate_pages(struct fscache_cache *cache)
 533 {
 534         _enter("");
 535 }
 536
 537 const struct fscache_cache_ops cachefiles_cache_ops = {
 538         .name                   = "cachefiles",
 539         .alloc_object           = cachefiles_alloc_object,
 540         .lookup_object          = cachefiles_lookup_object,
 541         .lookup_complete        = cachefiles_lookup_complete,
 542         .grab_object            = cachefiles_grab_object,
 543         .update_object          = cachefiles_update_object,
 544         .invalidate_object      = cachefiles_invalidate_object,
 545         .drop_object            = cachefiles_drop_object,
 546         .put_object             = cachefiles_put_object,
 547         .sync_cache             = cachefiles_sync_cache,
 548         .attr_changed           = cachefiles_attr_changed,
 549         .read_or_alloc_page     = cachefiles_read_or_alloc_page,
 550         .read_or_alloc_pages    = cachefiles_read_or_alloc_pages,
 551         .allocate_page          = cachefiles_allocate_page,
 552         .allocate_pages         = cachefiles_allocate_pages,
 553         .write_page             = cachefiles_write_page,
 554         .uncache_page           = cachefiles_uncache_page,
 555         .dissociate_pages       = cachefiles_dissociate_pages,
 556         .check_consistency      = cachefiles_check_consistency,
 557 };